Fourth and 19 on A's 21. A-2 illegally contacts B-3 on A's 18. Passer A-1 throws an interception to B-8 on B's 19. Runner B-8 (i) flag guards at B's 20 and is deflagged at B's 25; (ii) is deflagged at B's 25. What are ways this can be enforced?
In (i), if Team B accepts the illegal contact penalty, then it is Team A's ball at A's 21 and a replay fourth down. This is a double foul (Rule 10-3-3C) and the Referee should announce that both penalties offset. If Team B declines the penalty and Team A accepts the flag guarding penalty, then it's Team B's ball at B's 10.
In (ii), if Team B declines the illegal contact penalty, it is Team B's ball at B's 25. If Team B accepts the penalty, then it is Team A's ball at A's 11 and replay fourth down, double stakes.